This application claims the priority of German Application No. 100 26 032.2, filed May 25, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a device and a process for measuring distances and speeds and, in particular, for measuring distances and speeds between a motor vehicle and several objects, such as mobile targets (other motor vehicles) and fixed targets.
German Patent document DE 196 46 228 A1 describes a process for measuring the distance between two objects. According to this process, an object, for example a motor vehicle, emits radar signals FMCW (=frequency modulation continuous wave), which are reflected in part by a second object, e.g. from a leading vehicle. The reflected signal is picked up; and a differential signal is formed from both signals. The process, described in this patent, can be used especially in the near range and in the presence of several targets. The intermediate frequency signal is evaluated by means of the maximum entropy method.
German Patent document DE 42 44 608 A1 describes a radar system-based process for measuring distances and relative speeds between a motor vehicle and impediments in the direction of travel. This prior art process carries out four process steps altogether, wherein three measurements serve to detect potential impediments and a fourth measurement sorts out ghost and fictive impediments that are generated during the evaluation.
The present invention is based on the problem of providing a device and a process, with which it is possible to measure accurately the distance and/or the speed between a motor vehicle and several objects, while avoiding false detections.
This problem is solved by a device and process for measuring the distances and/or speeds between a motor vehicle and several objects, like mobile targets. The device includes: an FMCW radar system, where the motor vehicle transmits a signal, whose transmitting frequency is modulated with at least two frequency ramps; a device for detecting the receiving signals from the objects and for determining the respective straight lines and the intersecting points of these straight lines in a speed-distance diagram; a device for sorting out the intersecting points from fixed targets and the related straight lines; and a device for the output of the distances and/or the speeds, which correspond to the other intersecting points.
The invention proceeds from the basic idea of sorting out the radar signals, reflected from the fixed targets, during the evaluation process and of evaluating the measurement results for the mobile targets.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.